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Working with Genes: Analysing and Manipulating DNA  

This chapter explores the process of analysing and manipulating deoxyribonucleic acid (DNA). A wide range of molecular biology techniques enables DNA to be manipulated and analysed, yielding information about the nature and function of genes. The terms recombinant DNA technology, DNA cloning, and gene cloning all refer to the same process, namely the transfer of a DNA fragment from one organism to a self-replicating genetic element that replicates the fragment in a foreign host cell. Multiple copies of a DNA sequence can be produced by cloning or by using the polymerase chain reaction. Genes are isolated from DNA libraries and gel electrophoresis separates different-sized DNA fragments. Meanwhile, the nucleotide sequence of a segment of DNA is determined by Frederick Sanger’s dideoxy method or next generation sequencing methods. Finally, forward and reverse genetics are different analytical approaches to linking phenotype and genotype.

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Principles of Mendelian Inheritance  

This chapter examines the principles of Mendelian genetics, which is concerned with patterns of inheritance associated with one or a few genes. Monohybrid crosses investigate the genetic basis of traits determined by a single gene. Meanwhile, dihybrid crosses consider the inheritance patterns produced by the segregation of alleles of two genes. An individual possesses two alleles for each gene, which may be similar or different. Alleles segregate into gametes during meiosis. Next, the chapter looks at the relationship between probability and Mendelian genetics. The chi-squared statistical test is used in Mendelian genetics to compare observed progeny numbers with expected ratios, because the ratios of different progeny phenotypes can be informative of underlying genetics.

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The Genetics of Bacteria, Viruses, and Organelles  

This chapter assesses the genetics of bacteria, viruses, and organelles. It begins by looking at the bacterial genome; most bacteria have a single circular chromosome, several million nucleotides in length. Bacteria and viruses have small haploid genomes. They are well suited to genetic studies because they have high rates of reproduction and produce large numbers of progeny. Plasmids are often present in bacterial cytoplasm. The chapter then considers how DNA can be transferred between bacterial cells by conjugation, transformation, or transduction. Viruses have DNA or RNA genomes. Bacteriophages are DNA viruses that infect bacteria, while retroviruses are RNA viruses that infect eukaryotic cells. Mitochondria and chloroplasts have their own genetic systems.

Chapter

Cover Genomics

Genomes And Ethics  

This chapter examines some of the ethical implications of genomics, looking at how advances in genetics are likely to be experienced by people, as patients, consumers, and citizens. Our ability to sequence genomes is getting faster and cheaper all the time. Indeed, genomic technology is now being utilized in more settings across society than ever before, from medicine, population health screening, and recreational consumerism (ancestry testing, nutritional testing), through to policing and crime prevention. Given that genomic information links us to our relatives, the decisions that we make about it will all have an impact on those we are related to and the knowledge that they too can gain. It is this fact that makes genetic information quite different from other sorts of medical information. Thus, we all have a stake in how we as a society use genomic data.

Chapter

Cover Genetics

Human Genetic Mapping, Genome-wide Association Studies, and Complex Traits  

This chapter brings together fundamental concepts of genetics and genomes on complex traits and genome-wide association studies, which focus primarily on human traits and diseases. It explores genome-wide association studies in order to build upon the basic principles that identify contributing genes and causative mutations. It provides an approach that shows how genome-wide associations integrate genomic variation, complex phenotypes, and evolutionary history. The chapter mentions the Human Genome Project, which made it possible to identify hundreds of individual genes that affect disease phenotypes. It focuses on human genetic diseases and provides an analysis of the human genome, which allowed a much deeper understanding of many aspects of the overall biology of Homo sapiens.

Chapter

Cover Genetics

The Genetics of Populations  

This chapter delves into population genetics with a human focus and explores the assumptions of the Hardy—Weinberg equilibrium model. It reviews the many different types of evolutionary change which can operate in order to shape the genetic structure of a population and the imprints these leave at the level of the genome. It also features long-term studies of bacterial populations presented as a method to explore evolution experimentally. The chapter describes how transmission of alleles and genotypes within a population can be assessed, even when the individual matings cannot be monitored. It defines non-random mating as the main process that affects genotype frequencies without affecting allele frequencies directly, which can result in population stratification.

Book

Cover Genetic Analysis
Genetic Analysis applies the combined power of molecular biology, genetics, and genomics to explore how the principles of genetics can be used as analytical tools to solve biological problems. Opening with a brief overview of key genetic principles, model organisms, and epigenetics, the book goes on to explore the use of gene mutations and the analysis of gene expression and activity. A discussion of the genetic structure of natural populations follows, before the interaction of genes during suppression and epistasis, how we study gene networks, and personalized genomics are considered.

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Genetics of Populations  

This chapter examines population genetics, which analyses the patterns of genetic variation shown by groups of individuals, i.e. by populations. This contrasts with the main concern of Mendelian genetics and, to a large extent, of quantitative genetics, as both focus on the genotype of individuals and the genotypes resulting from single mating. Population genetics explores the evolutionary processes that shape a population’s genetic variation, i.e. mating systems, migration, mutation, population size, and selective forces. The chapter then considers how the analysis of genetic diversity in populations of endangered species helps formulate conservation policies. Ultimately, the genetic variation within and between different populations is described in terms of frequencies of alleles and resulting genotypes. The chapter looks at the Hardy–Weinberg equilibrium, non-random mating, natural selection, and genetic drift.

Chapter

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Quantitative Genetics  

This chapter focuses on quantitative genetics, which analyses the inheritance of complex traits. Complex traits are multifactorial: their expression is influenced by multiple genes and various environmental factors. Most complex traits exhibit continuous phenotypic variation and threshold traits exhibit just two phenotypes. Susceptibility to express a threshold trait is quantitative: it is determined by numerous genetic and environmental factors. The chapter also looks at the role of additive genes, the statistical analysis of continuous traits, heritability, human quantitative traits, and quantitative trait loci (QTL), which are genes that influence quantitative traits. Heritability values indicate the relative input of genetic and environmental factors in determining a phenotype.

Chapter

Cover Genetic Analysis

Reverse genetics  

Editing genes in yeast and mice

This chapter focuses on reverse genetics in which the start point is the DNA sequence of a cloned gene, and the mutant phenotype—and hence biological function of the gene—is inferred from that sequence. The chapter starts with an exploration of the reverse genetic analysis carried out on budding yeast and mice. It explores two approaches to reverse genetics: gene disruption and gene replacements. It includes a discussion of the Cre-lox system as an example of gene replacement achieved by site-specific recombination.